The present invention relates generally to microelectromechanical systems microphones. More particularly, this invention relates to a microelectromechanical system package for providing an environmental and interference shield to a microelectromechanical system microphone.
There have been a number of disclosures related to building microphone elements on the surface of a silicon die. Certain of these disclosures have come in connection with the hearing aid field for the purpose of reducing the size of the hearing aid unit. While these disclosures have reduced the size of the hearing aid, they have not disclosed how to protect the transducer from outside interferences. For instance, transducers of this type are fragile and susceptible to physical damage. Furthermore, they must be protected from light and electromagnetic interferences. Moreover, they require an acoustic pressure reference to function properly. For these reasons, the silicon die must be shielded.
Some shielding practices have been used to house these devices. For instance, insulated metal cans or discs have been provided. Additionally, DIPs and small outline integrated circuit (SOIC) packages have been utilized. However, the drawbacks associated with manufacturing these housings, such as lead time, cost, and tooling, make these options undesirable.
The present invention is related to a packaging for a microelectromechanical system (MEMS) microphone. The MEMS microphone package provides a shield for a MEMS microphone from an interference signal and/or environmental condition. The package generally comprises a MEMS microphone, a substrate and a cover.
One object of the invention is to provide such a package comprising a substrate having a surface for supporting the MEMS microphone, and a cover. The cover includes a conductive layer and a center portion bounded by a peripheral edge portion. A housing is formed by connecting the peripheral edge portion of the cover to the substrate. The center portion of the cover is spaced from the surface of the substrate to accommodate the MEMS microphone. The housing includes an acoustic port for allowing an acoustic signal to reach the MEMS microphone. The housing provides protection to the MEMS microphone from an interference signal.
Another object of the invention is to provide a MEMS package comprising a silicon-based microphone, a substrate, and a cover. The substrate includes a surface at least partially covered by a first layer of a conductive material. The silicon-based microphone is electrically coupled to the layer of a conductive material. The cover comprises a second layer of a conductive material. The cover is electrically connected to the first layer of a conductive material to provide a chamber in which the silicon-based microphone is located. The chamber provides an acoustic front volume for the silicon-based microphone.
Another object of the invention is to provide a package for a MEMS microphone. The package comprises a substrate, a first layer of a conductive material, as second layer of a conductive material, and an acoustic port. The substrate is produced from a non-conductive material and includes an upper surface. The first layer of a conductive material at least partially covers the upper surface of the substrate. The second layer of a conductive material is electrically connected to the first layer of a conductive material. The second layer of a conductive material comprises a peripheral edge portion that is at least partially sealed to the substrate and a central portion spaced from the upper surface of the substrate to provide a chamber. The acoustic port allows acoustic energy to enter the chamber.
Another object of the present invention is to provide a package for MEMS microphone comprising a substrate, a first layer of a conductive material, and a cover. The substrate is produced from a non-conductive material having an upper surface. The first layer of a conductive material at least partially covers the upper surface of the substrate. The cover includes a formed metal cup electrically connected to the first layer of a conductive material. The formed metal cup comprises a peripheral edge portion at least partially sealed to the substrate and a central portion spaced from the upper surface of the substrate to provide a chamber. The acoustic port allows acoustic energy to enter the chamber.
Another object of the present invention is to provide a MEMS package comprising a MEMS microphone, a substrate, a cover, and a housing. The substrate comprises a surface for supporting the MEMS microphone. The cover has a central portion bounded by a peripheral edge, and comprises a first formed metal cup and a second metal cup fit within the first metal cup in mating relationship. The cover further comprises an environmental barrier layer disposed between the first and second metal cups. The housing is formed by connecting the peripheral edge portion of the cover to the substrate. The center portion of the cover is spaced from the surface of the substrate to accommodate the MEMS microphone. The housing includes an acoustic port for allowing an acoustic signal to reach the MEMS microphone wherein the housing provides protection from an interference signal.
Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawings.